Sex Differences

The question as to the relative intelligence of the
sexes is one of perennial interest and great social importance. The
ancient hypothesis, the one which dates from the time when only men
concerned themselves with scientific hypotheses, took for granted the
superiority of the male. With the development of individual psychology,
however, it was soon found that as far as the evidence of mental tests
can be trusted the _average_ intelligence of women and girls is as high
as that of men and boys.

If we accept this result we are then confronted with the difficult
problem of finding an explanation for the fact that so few of those who
have acquired eminence in the various intellectual fields have been
women. Two explanations have been proposed: (1) That women become
eminent less often than men simply for lack of opportunity and stimulus;
and (2) that while the average intelligence of the sexes is the same,
extreme variations may be more common in males. It is pointed out that
not only are there more eminent men than eminent women, but that
statistics also show a preponderance of males in institutions for the
mentally defective. Accordingly it is often said that women are grouped
closely about the average, while men show a wider range of distribution.

Many hundreds of articles and books of popular or quasi-scientific
nature have been written on one aspect or another of this question of
sex difference in intelligence; but all such theoretical discussions
taken together are worth less than the results of one good experiment.
Let us see what our 1000 I Q's have to offer toward a solution of the
problem.

1. When the I Q's of the boys and girls were treated separately there
was found a small but fairly constant superiority of the girls up to the
age of 13 years. At 14, however, the curve for the girls dropped below
that for boys. This is shown in Figure 3.

The supplementary data, including the teachers' estimates of
intelligence on a scale of five, the teachers' judgments in regard to
the quality of the school work, and records showing the age-grade
distribution of the sexes, were all sifted for evidence as to the
genuineness of the apparent superiority of the girls age for age. The
results of all these lines of inquiry support the tests in suggesting
that the superiority of the girls is probably real even up to and
including age 14, the apparent superiority of the boys at this age being
fully accounted for by the more frequent elimination of 14-year-old
girls from the grades by promotion to the high school.

2. However, the superiority of girls over boys is so slight (amounting
at most ages to only 2 to 3 points in terms of I Q) that for practical
purposes it would seem negligible. This offers no support to the opinion
expressed by Yerkes and Bridges that "at certain ages serious injustice
will be done individuals by evaluating their scores in the light of
norms which do not take account of sex differences."

3. Apart from the small superiority of girls, the distribution of
intelligence in the two sexes is not different. The supposed wider
variation of boys is not found. Girls do not group themselves about the
median more closely than do boys. The range of I Q including the middle
fifty per cent is approximately the same for the two sexes.

4. When the results for the individual tests were examined, it was found
that not many showed very extreme differences as to the per cent of boys
and girls passing. In a few cases, however, the difference was rather
marked.

The boys were decidedly better in arithmetical reasoning, giving
differences between a president and a king, solving the form board,
making change, reversing hands of clock, finding similarities, and
solving the "induction test." The girls were superior in drawing designs
from memory, aesthetic comparison, comparing objects from memory,
answering the "comprehension questions," repeating digits and sentences,
tying a bow-knot, and finding rhymes.

Accordingly, our data, which for the most part agree with the results of
others, justify the conclusion that the intelligence of girls, at least
up to 14 years, does not differ materially from that of boys either as
regards the average level or the range of distribution. It may still be
argued that the mental development of boys beyond the age of 14 years
lasts longer and extends farther than in the case of girls, but as a
matter of fact this opinion receives little support from such tests as
have been made on men and women college students.

The fact that so few women have attained eminence may be due to wholly
extraneous factors, the most important of which are the following: (1)
The occupations in which it is possible to achieve eminence are for the
most part only now beginning to open their doors to women. Women's
career has been largely that of home-making, an occupation in which
eminence, in the strict sense of the word, is impossible. (2) Even of
the small number of women who embark upon a professional career, a
majority marry and thereafter devote a fairly large proportion of their
energy to bearing and rearing children. (3) Both the training given to
girls and the general atmosphere in which they grow up are unfavorable
to the inculcation of the professional point of view, and as a result
women are not spurred on by deep-seated motives to constant and
strenuous intellectual endeavor as men are. (4) It is also possible that
the emotional traits of women are such as to favor the development of
the sentiments at the expense of innate intellectual endowment.